pyridine hydrobromide

Acid has various chemical properties. Its taste is more acidic, and it can make litmus test solution turn red, which is a well-known sign.
In water, acid can dissociate hydrogen ions, which is its key characteristic. Take hydrochloric acid as an example, it will dissociate quickly in water, releasing a large number of hydrogen ions and chloride ions, so that the solution is acidic. When acid and base meet, they often neutralize, and the two are synthesized into salt and water. This reaction is like the combination of yin and yang, each taking what he needs, and the acid and base neutralize and return to peace. For example, when hydrochloric acid is mixed with sodium hydroxide, the hydrogen ion of hydrochloric acid combines with the hydroxide ion of sodium hydroxide to form water, and the remaining sodium ion and chloride ion form sodium chloride, which is the common table salt.
Acid and metal also have a wonderful reaction. Active metals are often eroded when they encounter acid. Metal atoms lose electrons and become metal ions that dissolve into solution. At the same time, hydrogen ions in the acid gain electrons and become hydrogen gas to escape. If zinc flakes are put into dilute sulfuric acid, bubbles will pop up immediately, and zinc will gradually dissolve. This is the reaction between zinc and sulfuric acid to form zinc sulfate and hydrogen.
Furthermore, acid also has a role in metal oxides. It can react with it to form salts and water. Iron oxide, the main component of rust, is soluble in acid. Acid reacts with iron oxide to convert it into iron salts and water, which means that acid can remove rust.
In addition, acid often acts as a catalyst in chemical reactions, which can accelerate many reaction processes. Although the quantity and quality remain unchanged before and after the reaction, it can change the reaction rate. For example, some organic reactions can be carried out more efficiently with acid catalysis. This is the chemical properties of acids. In the field of chemistry, acids have a wide range of effects and far-reaching effects.

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Strontium carbonate has a significant effect on ceramics. In ceramic glazes, the addition of strontium carbonate can make the glaze surface smoother and enhance its wear resistance and chemical resistance. The ceramic utensils are not only beautiful in appearance, but also durable. For example, the exquisite porcelain produced by the official kiln, in the glaze formula, or the clever use of strontium carbonate, can achieve the brilliant color and texture.
Furthermore, glass manufacturing is also an important application of strontium carbonate. In the glass production process, adding an appropriate amount of strontium carbonate can improve the chemical stability and mechanical strength of the glass. The quality of these glass products, such as window glass, optical glass, etc., has been greatly improved. In the past, craftsmen wanted to make high-quality optical glass. After repeated trials, they finally found the wonderful use of strontium carbonate here, laying the foundation for the development of optical instruments.
In the field of electronics industry, strontium carbonate is also indispensable. For example, in the manufacture of electronic components, cathode ray tubes, etc., strontium carbonate is an important raw material. Due to its special physical and chemical properties, it can help electronic components to better perform and ensure the stable operation of electronic equipment. Although there was no electronic industry in ancient times, if we look back in today's perspective, the characteristics of these materials seem to be in line with the principles of natural creation.
In the manufacture of fireworks, strontium carbonate also has extraordinary performance. Because it can make the flame appear bright red, it is often used in the production of fireworks. During festivals, when brilliant fireworks bloom in the night sky, strontium carbonate plays a role in creating beautiful colors and adding endless joy to festivals.
In addition, in the metallurgical industry, strontium carbonate can be used as a desulfurizer to remove sulfur impurities in metals, improve metal purity and improve metal properties. This is also like the ancient sword, which needs to be tempered and removed in various ways to cast a sharp blade. Strontium carbonate is used in metallurgy, which is like the key step to remove barren and save cyanine.

There are various methods for preparing hydrochloric acid. In the past, it was mostly obtained by co-heating table salt and sulfuric acid. The method is as follows: Take table salt and put it in a kettle, gradually inject sulfuric acid, and heat it. The reason for the reaction is that the sulfuric acid is strong, and it interacts with sodium chloride in table salt to produce hydrogen chloride gas. This gas meets water to form hydrochloric acid. Its chemical formula is about $2NaCl + H_ {2} SO_ {4}\ stackrel {\ Delta }{=\!=\!=} Na_ {2} SO_ {4} + 2HCl\ uparrow $. After the hydrogen chloride escapes, it is introduced into the water to obtain hydrochloric acid.
There are other methods. In industry, hydrogen and chlorine are often combined to produce hydrochloric acid. Hydrogen and chlorine are first purified, and then in a special vessel, the two meet and burn. Chlorine is yellow and poisonous, hydrogen is light and flammable, and the two burn together, giving rise to a pale flame, generating hydrogen chloride gas. The reaction formula is $H_ {2} + Cl_ {2}\ stackrel {ignited }{=\!=\!=} 2HCl $. The resulting hydrogen chloride is also introduced into water to form hydrochloric acid. The hydrochloric acid obtained by this method is more pure than those made of table salt and sulfuric acid.
Furthermore, hydrochloric acid is also obtained from by-products of organic chlorination. For example, in organic synthesis, some reactions will produce hydrogen chloride, which can be collected and dissolved in water to form hydrochloric acid. However, the hydrochloric acid obtained by this method, or containing impurities, needs to be refined. In short, the methods of making hydrochloric acid have their own advantages and disadvantages, and the appropriate one should be selected according to the required amount and purity.

To test the purity of hydrochloric acid, follow the following methods.
Take an appropriate amount of hydrochloric acid sample first, and measure its volume with an accurate measuring instrument. Then, use a standard alkali solution of known concentration, such as sodium hydroxide solution, for titration.
When titrating, drop a few drops of a suitable indicator, such as phenolphthalein, into the hydrochloric acid test solution. This indicator does not change color in case of acid, but changes color in case of alkali. When the standard alkali is slowly dripped, gently shake the test solution while dripping to fully mix the reaction.
The color of the test solution just has a significant and lasting change, that is, the titration end point is reached. Record the volume of the standard alkali solution consumed at this time.
According to the reaction principle of acid-base neutralization, the stoichiometric relationship between hydrochloric acid and sodium hydroxide is clear. Let the amount and concentration of the substance of hydrochloric acid be\ (c_ {HCl}\), the volume is\ (V_ {HCl}\), the amount and concentration of the substance of the sodium hydroxide standard solution is\ (c_ {NaOH}\), the consumption volume is\ (V_ {NaOH}\), and the reaction equation is\ (HCl + NaOH = NaCl + H_ {2} O\). It can be seen that\ (n_ {HCl} = n_ {NaOH}\), that is,\ (c_ {HCl} V_ {HCl} = c_ {NaOH} V_ {NaOH}\).
From this, the concentration of the substance in hydrochloric acid can be calculated\ (c_ {HCl} =\ frac {c_ {NaOH} V_ {NaOH}} {V_ {HCl}}\).
The purity of hydrochloric acid requires knowing the density of its solution\ (\ rho\), first calculate the mass of the solute\ (HCl\) in the hydrochloric acid solution\ (m_ {HCl} = c_ {HCl} V_ {HCl} M_ {HCl}\) (\ (M_ {HCl}\) is the molar mass of\ (HCl\)), the mass of the solution\ (m =\ rho V_ {HCl}\), then the purity of hydrochloric acid\ (\ omega =\ frac {m_ {HCl}} {m}\ times100\% =\ frac {c_ {{HCl} V_ {HCl} M_ {HCl}} {\ rho V_ {HCl}}\ times100\% =\ frac {c_ {HCl} M_ { HCl}} {\ rho}\ times 100 \%\) 。
In this way, the purity of hydrochloric acid can be determined.

When I asked, I asked him what the conditions for the storage of the medicine were. Although this matter is not detailed in "Tiangong Kaiwu", it can be inferred according to various pharmacology and the storage methods of the ancients.
Ancient storage of medicine, the first dry environment. Wet is easy to cause the medicine to mildew and rot, and damage its medicinal power. Therefore, it is often placed in a high open and dry place, away from water and moisture. For example, the medicine storehouses of the Beijing Shitai Hospital are all built in high-lying and well-ventilated places, so that the medicine is always clear and not invaded by moisture.
Second, it is protected from light. Light can easily dissipate or mutate the medicinal power. It is mostly hidden in dark places, or blocked by cloth, so as not to allow direct sunlight. And the medicine may be contained in boxes and clay jars, and the lid is tightly sealed to prevent the disturbance of light and air. Fragrances such as musk must be stored tightly in porcelain jars and placed in a dark room to prevent their aroma from escaping and their potency from attenuating.
Furthermore, temperature is also important. If it is overheated, the medicine will easily evaporate, and if it is too cold, the quality of the medicine may change. The ancients often adjusted the storage place according to the change of seasons. When it is hot, choose a cool place; when it is cold in winter, keep warm. There are also those hidden in the cellar, because of its constant temperature and humidity, which is conducive to the long-term storage of the medicine.
The separate storage of the medicine is also an important rule. Agents of different medicinal properties cannot be mixed. Those who are dry and moisturized should be stored separately to avoid mutual influence. Poisonous agents need to be stored separately and strictly guarded to prevent them from accidentally taking and hurting people.
Although "Tiangong Kaiwu" does not specify the details of the storage of medicines, the ancients used the art of health and treatment with good intentions, and the method of storage has also been pondered for generations.